/*
 * Copyright 2012 Gregor Schauer
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package at.schauer.gregor.vienna.identifier;

import java.util.Map;
import java.util.WeakHashMap;

/**
 * @author Gregor Schauer
 */
public abstract class CachedGenerator<I, O> implements IdentifierGenerator<I, O> {
	protected final Map<O, I> cache = new WeakHashMap<O, I>();

	@Override
	public I generate(O obj) {
		if (!cache.containsKey(obj)) {
			synchronized (cache) {
				if (!cache.containsKey(obj)) {
					cache.put(obj, newIdentifier(obj));
				}
			}
		}
		return cache.get(obj);
	}

	protected abstract I newIdentifier(O obj);
}
